Botensilimab, an Fc-Enhanced Anti–CTLA-4 Antibody, Is Effective against Tumors Poorly Responsive to Conventional Immunotherapy

Abstract Conventional immune checkpoint inhibitors (ICI) targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4) elicit durable survival but primarily in patients with immune-inflamed tumors. Although the mechanisms underlying response to anti–CTLA-4 remain poorly understood, Fc-gamma receptor (FcγR) IIIA coengagement seems critical for activity, potentially explaining the modest clinical benefits of approved anti–CTLA-4 antibodies. We demonstrate that anti–CTLA-4 engineered for enhanced FcγR affinity leverages FcγR-dependent mechanisms to potentiate T-cell responsiveness, reduce intratumoral regulatory T cells, and enhance antigen-presenting cell activation. Fc-enhanced anti–CTLA-4 promoted superior efficacy in mouse models and remodeled innate and adaptive immunity versus conventional anti–CTLA-4. These findings extend to patients treated with botensilimab, an Fc-enhanced anti–CTLA-4 antibody, with clinical activity across multiple poorly immunogenic and ICI treatment–refractory cancers. Efficacy was independent of tumor neoantigen burden or FCGR3A genotype. However, FCGR2A and FCGR3A expression emerged as potential response biomarkers. These data highlight the therapeutic potential of Fc-enhanced anti–CTLA-4 antibodies in cancers unresponsive to conventional ICI therapy. Significance: This study reveals that Fc-enhanced anti–CTLA-4 harnesses novel mechanisms to overcome the limitations of conventional anti–CTLA-4, effectively treating poorly immunogenic and treatment-refractory cancers. Our findings support the development of a new class of immuno-oncology agents, capable of extending clinical benefit to patients with cancers resistant to current immunotherapies.